The High-speed Fiber Grating Demodulation Technology And Experimental Research Based On FPGA

In recent years,while vigorously promoting the transformation of old and new driving forces,the state has vigorously supported the research on new materials and new processes,and promoted the new development pattern of intelligent and networked information technology.As a new material,Fiber Bragg Grating(FBG)has become the research focus of experts at home and abroad,and the sensing technology based on FBG has also been vigorously developed.FBG sensors have many more outstanding characteristics that compare with conventional sensors.Due to their many advantages including anti-electromagnetic interference,electrical insulation,acid and alkali corrosion resistance,small size,light weight and high sensitivity,FBG sensors are widely used in seismic monitoring,civil engineering,aerospace,marine exploration,petrochemical and other fields.The demodulation technology of sensing signals has always been a major obstacle to the application of FBG.Many technologies are limited to the stage of laboratory research.Although there are related products of FBG sensing demodulation based on different solutions at home and abroad,most of products exist some shortcomings,such as low demodulation frequency,complex structure and high price,which is difficult to meet the requirements of high-frequency signal state monitoring and limits the engineering application of FBG.In contrast,the hardware system based on the field programmable gate array FPGA can fully utilize the advantages of high speed,high customization,simple structure,achieving low-cost high-speed demodulation of FBG.Therefore,aiming at the problems of FBG sensor demodulation equipment,this paper based on the basic principle of FBG sensing theory analyzes and studies the demodulation scheme of FBG in detail.The high-speed FBG demodulation system based on FPGA is designed and a complete experimental test is performed.The main research contents and results are as follows:Firstly,according to the research status of fiber grating sensing technology,the principle and characteristics of fiber grating sensing are introduced.After comparing several common fiber grating demodulation methods,the edge linear filtering method is selected as the sensing demodulation method in this paper.The optical path of the fiber grating demodulation system based on linear filter is designed,and the structures and performances of each part are briefly introduced.Secondly,a grating vibration sensor with simply supported beam structure is designed and fabricated.The fabrication and packaging process of the sensor is introduced in detail.The physical model of the sensor structure is analyzed,and the mathematical relationship between the reflection wavelength,the physical structure of the sensor and the external vibration parameters is deduced.Thirdly,the high-speed demodulation signal acquisition system with FPGA is designed as the control core,which makes full use of the advantages of flexible parallel structure and high-speed data processing of the FPGA.The hardware circuit and software driver of the lower-computer including AD acquisition,dual-port RAM access and Ethernet data transmission are designed.Meanwhile,the demodulation processing software of upper-computer is developed by Labview,which provides the functional verification of the demodulation system.Finally,the overall demodulation scheme,sensor design and the performance of the acquisition and processing system are fully tested.The experimental results of the designed demodulation system and standard SM130 are compared and analyzed.Experiments show that the demodulation system of high-speed FBG based on FPGA achieves the requirements of high integration and high resolution demodulation system.The overall performance of the system is stable and reliable,and meets the design requirements.This demodulation system will promote the application of FBG sensors in the field of high-frequency signal monitoring.